Variable wall thickness for delivery sheath housing

ABSTRACT

A delivery sheath for an intravascular emboli capturing filter including an elongate tube having a distal region having a reduced thickness distal wall region. The delivery sheath, according to the present invention, can have a thinner, softer, distal most portion for superior and more benign interaction with vessel interior walls. The present invention includes an intravascular emboli filter system including an elongate shaft having a distal region, an expandable emboli filter operably coupled to the elongate shaft distal region, and an elongate sheath having a lumen therethrough disposed over the elongate shaft. The elongate sheath can have a distally decreasing outside diameter taper or reduced wall thickness region having improved atraumatic characteristics.

RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 10/749,270 filed Dec. 31, 2003, which is a continuation applicationof U.S. application Ser. No. 09/770,030 filed Jan. 25, 2001, now U.S.Pat. No. 6,689,151.

FIELD OF THE INVENTION

The present invention is related generally to medical devices. Morespecifically, the present invention includes tubular sheaths fordelivering intravascular blood filtering devices.

BACKGROUND OF THE INVENTION

Blood vessels can become occluded in several ways. In one situation, astenosis may be formed of an atheroma which can include a calcifiedmaterial formed on the lumen walls of the blood vessel. In anothersituation, a stenosis can be formed of a thrombosis material which istypically softer than the calcified material, but can cause sudden andunpredictable blood flow reduction in a blood vessel lumen.

Different procedures have been developed to treat a stenotic lesion orstenosis in the vasculature. One method includes deforming the stenosisto reduce the restriction within the lumen of the blood vessel. Thistype of deformation is typically performed using balloon angioplasty.Another method includes the attempted removal of the stenosis or part ofthe stenosis. Removal of the stenotic lesion can be attempted throughuse of atherectomy, which can include mechanical ablation, radiofrequency energy removal, and laser removal. In these methods, thestenosis can be mechanically cut or ablated from the vessel.

Problems may be encountered by the treating physician duringthrombectomy and atherectomy. Stenotic debris, which may be separatedfrom the stenosis, may be freed within the lumen of the vessel. If thedebris flows distally, it can occlude distal vasculature and causeproblems. If it flows proximally, it can enter the circulatory systemwhich is also undesirable.

One technique for dealing with such debris includes filtering orotherwise removing the debris from within the vessel using anintravascular capture device. In one such method, a filtering device maybe disposed distal of the stenosis during an atherectomy to catch theemboli or pieces of stenosis as they are released. These pieces oremboli may be removed using the capture device when the atherectomyprocedure is complete. One such capture device includes a distalexpandable filter member which can be placed distal of the stenosis tocapture stenosis fragments. Expandable devices may be delivered througha delivery sheath and/or guide catheter to the treatment site. Thedelivery sheath and/or guide catheter may be retracted proximally priorto deploying the filter. After use, the filter may be retracted into thedelivery sheath or guide catheter for removal.

What would be desirable are improved delivery sheaths for deliveringdistal protection devices to the treatment site. In particular, morebenign delivery sheaths with distal ends that are easier to steer wouldbe desirable.

SUMMARY OF THE INVENTION

The present invention includes delivery sheaths for intravascular embolicapturing filters, the sheath including an elongate tube having a distalregion wall that is distally decreasing in thickness. In one embodiment,the distally decreasing wall thickness is imparted at least in part by adistally decreasing outside sheath diameter. In some embodiments, atapered distal region forms a region of increasing softness relative tothe more proximal adjacent region. One example of an expandable embolifilter is provided by U.S. Pat. No. 5,827,324, herein incorporated byreference.

The present invention includes intravascular emboli filtering systemsincluding an elongate shaft having an expandable emboli filter operablycoupled to the shaft distal region. The system can further include anelongate sheath having a lumen therethrough for slidably accepting theexpandable emboli filter in a collapsed state. The elongate sheathpreferably has a tapered, distal region having a distally decreasingwall thickness. In one embodiment, the distally decreasing wallthickness is accomplished with a distally decreasing outside diameter.One embodiment includes a substantially sudden decrease in wailthickness at the distal region, rather than a gradual taper.

In use, the emboli filter may be collapsed, and disposed within thedelivery sheath distal region. A guidewire may be advanced into thepatient's vasculature and advanced further until the guidewire distalend is near the treatment site. In one method, the shaft of the embolifilter device serves as the guidewire. In another embodiment, aguidewire is first inserted, followed by the advancement of an embolifilter hollow shaft over the guidewire to a position distal of thetreatment site. The emboli filter, in the collapsed state, within thedelivery sheath, can be advanced together with the delivery sheath to aposition near, and preferably distal of, the treatment site. The embolifilter may be advance distally out of the delivery sheath. In onemethod, the emboli filter is advanced distally, while the deliverysheath is held in substantially constant position. In another method,the emboli filter is held in substantially constant position, while thedelivery sheath is proximally retracted.

The emboli filter, in an expanded configuration, may be left in placefor the treatment process. The emboli filter may be used in conjunctionwith atherectomy or angioplasty procedures. After a procedure, theemboli filter may be collapsed, followed by retracting the emboli filterinto the delivery sheath distal region. The emboli filter and deliverysheath may be retracted together and removed proximally from thepatient's vasculature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal, cross-sectional view of a distal protectiondevice within a vessel, shown in an expanded state, after advancementfrom within a delivery sheath;

FIG. 2 is a longitudinal, cross-sectional view of the distal protectiondevice of FIG. 1, shown in a collapsed state, after partial retractionwithin a delivery sheath;

FIG. 3 is a longitudinal, cross-sectional view of a delivery sheathdistal region; and

FIG. 4 is a side view of a delivery sheath in a process of manufacture.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates protection device 10 in a deployed, expandedposition. Protection device 10 preferably includes a shaft or hollowguidewire 18, or a hypotube having the same general dimensions as aguidewire, having a coil tip 19, and a capturing assembly 17 which caninclude strut distal ends 22, strut proximal ends 24, a plurality ofstruts or wires 20, mesh 26 and inflatable member 28. The plurality ofstruts or wires 20 can be operably coupled to a distal region of shaftor hollow guidewire 18. The connection is preferably a hinge-typeconnection, so that the struts 20 have distal ends 22 coupled closelyproximate the outer diameter of hollow guidewire 18 and proximal ends24. When deployed, proximal ends 24 can be pivoted radially away fromhollow guidewire 18. Mesh 26 is preferably formed of woven, knitted, orbraided fibers or wires or other suitable filtering or netting-typematerial. Portions of mesh 26 can extend between struts 20. Inflatablemember 28 is preferably coupled in fluid communication with an innerlumen which can run longitudinally within hollow guidewire 18.

Hollow guidewire 18 also preferably has a valve 30 coupled in a proximalportion thereof. During operation, a syringe is preferably connected tothe proximal end of guidewire 18, which preferably includes afluid-filled hypotube. The syringe is used to pressurize the fluid suchthat fluid is introduced through the lumen of hollow guidewire 18,through valve 30, and into inflatable member 28. Upon being inflated,inflatable member 28 preferably drives struts 20 to assume a deployedposition in which ends 24 are pivotally or otherwise moved radially awayfrom hollow guidewire 18 to a diameter which approximates the innerdiameter of lumen 12. In this way, capturing assembly or filter 17 isdeployed distally of stenosis 14 so that stenosis 14 can be severed andfragmented, and the fragments from stenosis 14 carried by blood flow,indicated by arrow 16, into the basket or chamber formed by the deployedfilter 17. Filter 17 can then be collapsed and removed from vessel 12with the fragments contained therein.

A delivery sheath 50, illustrated in phantom in FIGS. 1 and 2, may beseen to be slidably disposed over guidewire 18 and be cooperativelysized so as to contain protection device 10 in a collapsed state.Delivery sheath 50 may be seen to have a distal region 54, a distal end56, and has a lumen 52 therethrough. As illustrated in FIG. 1,protection device 10 has already been advanced from delivery sheath 50,and has been deployed.

FIG. 2 illustrates protection device 10 with filter 17 in the collapsedposition. Items in FIG. 2 are similarly numbered to those shown inFIG. 1. FIG. 2 illustrates that mesh 26 is collapsible beneath struts20. In order to collapse filter 17, fluid is preferably removed frominflatable member 28 through the lumen of hollow guidewire 18 andthrough two-way valve 30. This can be done using the syringe to pull avacuum or using any other type of suitable fluid removal system.

Struts 20 are preferably formed of a resilient material which has someshape memory. Thus, when inflatable member 28 is collapsed, struts 20can also collapse to approximate the outer diameter of hollow guidewire18. In another preferred embodiment, struts 20 are fastened toinflatable member 28 through adhesive, or another suitable connector, sothat they are effectively pulled to the collapsed position shown in FIG.2 when the fluid is removed from inflatable member 28. In yet anotherpreferred embodiment, inflatable member 28 is formed of a resilient,shape memory material. In that embodiment, inflatable member 28 isinflated by introducing fluid under pressure through the lumen in hollowguidewire 18, and into inflatable member 28. When pressure is releasedfrom the lumen in hollow guidewire 18, inflatable member 28 is allowedto force fluid out from the interior thereof through two-way valve 30and to resume its initial collapsed position. Again, this can result infilter 17 assuming its collapsed position illustrated by FIG. 2. In FIG.2, delivery sheath 50 may be seen to contain device 10, which has beencollapsed. Delivery sheath 50 may be seen to entirely contain protectiondevice 10.

FIG. 3 illustrates a side view of delivery sheath 50, including distalregion 54 having a length indicated by “L”. As illustrated in FIG. 3,distal region 54 has a distally tapering wall thickness indicated by aproximal wail thickness “D1” and a smaller distal wall thicknessindicated by “D2”. In the embodiment illustrated, the distally taperingwall thickness is imparted by distally decreasing the outside diameterof the sheath. In some embodiments, the distally decreasing wallthickness imparts a distally increasing softness to the delivery sheathdistal region. The delivery sheath tapering distal region length L isless than 10 millimeters in one embodiment, less than 5 millimeters inanother embodiment, less than 2 millimeters in yet another embodiment,and is less than one millimeter in a preferred embodiment.

In one embodiment, proximal wall thickness D1 is about 0.002 inch,distal wall thickness D2 is about 0.001 inch, and distal region length Lis about 1 millimeter. In one embodiment, not requiring separateillustration, the transition from proximal wall thickness D1 to distalwall thickness D2 is a substantially sudden step decrease, rather than agradual taper.

FIG. 4 illustrates a delivery sheath 70. Delivery sheath 70 is shown inan intermediate stage of manufacture, prior to grinding and removal of adistal region of the sheath. Sheath 70 includes a sheath proximal region84, a first intermediate region 82, a second intermediate region 83,followed by a distal portion 72. Distal portion 72 includes generally adistal region 74, a reduced diameter region 78, and a distal tip region80.

In one embodiment, sheath proximal region 84 has an inside diameter of0.0200 inch and a 0.0260-inch outside diameter, being expanded at afirst flared region 86 to an outside diameter of 0.0290 inch in sheathfirst intermediate region 82. In this embodiment, sheath secondintermediate region 83 has an outside diameter of 0.0310 inch increasingto an outside diameter of 0.0395 inch in sheath distal region 74 afteran increase at a second flared region 88. In one embodiment, distalportion 72 has a wall thickness of 0.0022 inches in distal region 74,decreasing to a wall thickness of 0.0011 inch in sheath reduced diameterregion 78 including far distal region 76. In one embodiment, sheathfirst intermediate region 82 has a length of about 0.100 inch, followedby sheath second intermediate region 83 having a length of about 0.25inch, with sheath second intermediate region 83 and sheath distal region74 together having a length of about 15 millimeter. In one embodiment,sheath far distal region 76 has a length of about 1 millimeter.

Sheath 70 can be manufactured by forming the intermediate stagesubstantially as illustrated in FIG. 4 from materials which can includepolymeric materials such as polyether copolymers or nylons.Specifically, a tube can be formed having the aforementioned featuresand dimensions, including a closed distal tip region 80. The closed endtube can be ground using centerless grinding techniques well known inthe art. Reduced diameter region 78 can be ground using the centerlessgrinding techniques until the wall thickness has been reduced relativeto the proximal end of distal region 74. The sheath, after grinding, maybe inserted into a mold and, using injection or blow molding techniques,the intermediate stage sheath may be molding to the desired shape. Themolded sheath may then be removed from the mold, having the molded shapeand further having reduced wall thickness distal region 78. The reducedwall thickness region 78 may then be partially removed by severing allbut a small proximal region of the reduced diameter region, thus leavingthe sheath with a small, reduced wall thickness distal region 76. In oneembodiment, sheath far distal region 76 has been both reduced in wallthickness by grinding, and has had the more distal section severed,leaving sheath far distal region 76 as a remaining, short, reduced wallthickness region. In one embodiment, sheath far distal region 76 is areduced wall thickness distal region having increased flexibilityrelative to the more proximal regions. The sheath formed by thecenterless grinding, blow molding, and severing of the distal region maybe ultimately used as a sheath for delivery and removal of an embolifilter.

Numerous advantages of the invention covered by this document have beenset forth in the foregoing description. It will be understood, however,that this disclosure is, in many respects, only illustrative. Changesmay be made in details, particularly in matters of shape, size, andarrangement of parts without exceeding the scope of the invention. Theinvention's scope is, of course, defined in the language in which theappended claims are expressed.

1. A delivery sheath for an intravascular emboli capturing filtercomprising: an elongate tube having a distal region, a distal end, and alumen therethrough, wherein said distal region has a length and a distalregion wall having a thickness, wherein said distal region wallthickness is distally decreasing.